A voice coil plate used in a flat type speaker is wound in an elliptical form and print-patterned on one side or both sides of a coil base of a plate form.
When current flows through a voice coil, the voice coil plate generates a magnetic field that is expanded and contracted around the voice coil in the same frequency as that of an audio signal by means of the flowing current. Since the magnetic field generated from the magnets within the speaker unit is applied to the voice coil, the voice coil plate moves up and down in response to the magnetic field while interacting with the magnetic field generated from the voice coil. Since the voice coil plate is connected to the vibration plate of the speaker unit, the vibration plate pushes air by way of the up and down movements and thus sound is generated by the vibration of the air.
Such a flat type speaker is being developed to have a gradually slim and long structure in line with an increase of an output capacity. Furthermore, in order to increase the output capacity of the flat type speaker, the development of a flat type speaker having a plurality of magnetic circuits connected emerges as an important problem.
In the case of voice coil film stacked in multiple layers, the number of turns needs to be increased to a maximum extent in order to increase induced electromotive force, but this is inefficient because a resistance value is increased in response to an increase of the number of turns. If a resistance value is preset, induced electromotive force cannot be increased because the number of turns cannot be increased, with the result that there is a difficulty in implementing a high-output speaker.